Catheter-based cryoablation of atrial fibrillation: state of the art.

Catheter-based ablation has been adopted as second-line therapy for both paroxysmal and persistent atrial fibrillation (AF) and is currently investigated as a primary approach. Reported success rates of catheter-based radiofrequency (RF) ablation vary between 65% and 85% depending on the technique used, patient selection and experience of the center. However, catheter ablation of AF is not without risk. In a worldwide survey major complications were reported in up to 6% of the procedures. Also, in high volume centers a complication rate of 5% is reported, which declined after excluding the learning curve during the first 100 procedures to 4.3%. These complications and the observation that AF-ablation using RF-energy is a demanding procedure in terms of operator competency and dexterity limiting the world-wide availability of this therapy lead to an extensive search for alternative energy and delivery sources. In four studies from Europe the new cryoballoon approach is effective and safe and appears to have a similar success rate than RF-ablation at least in paroxysmal AF and normally sized left atria. Changes in catheter design and additional equipment will probably improve this technique. Further clinical studies should focus on a head-to-head comparison between cryoablation and RF-ablation in AF. The favou-rable risk profile of cryoenergy might pave the way for cryoballoon ablation as a first-line treatment option in patients with paroxysmal AF.

Effect of ethanol on cardiac single sodium channel gating.

Alcohol in modest and higher doses has the potential to induce cardiac arrhythmias. The most famous alcohol-related arrhythmia is the "holiday heart syndrome". Furthermore, there is a clear association between excessive alcohol consumption and the risk of sudden cardiac death. However, the acute effects of ethanol on arrhythmia induction are not well understood. The effect of ethanol on single cardiac sodium channels has not been studied yet. To elucidate the effect of ethanol on human cardiac sodium channels we performed a patch clamp study in HEK-293 cells overexpressing the human cardiac sodium channel. We used HEK-293 cells overexpressing the human cardiac sodium channel (Na(1.5)). Single channel gating was investigated by the cell-attached patch clamp technique. Sodium channel currents were elicited by depolarizing pulses from -120 to -20mV for a duration of 150ms. Single channel availability, open probability and peak average current were assessed baseline and after addition of ethanol in increasing concentrations (0.50 per thousand (10.9mM), 1.00 per thousand (21.7mM), 2.00 per thousand (43.5mM) and 4.00 per thousand (87.0mM)). We found a concentration-dependent reduction of open probability which was statistically significant at 2.00 per thousand ethanol (66.5+/-14% of control). At higher concentrations (4.00 per thousand) also availability decreased to 66.5+/-11.0% of control. This resulted in a significant decrease of peak average current at 2.00 per thousand and at 4.00 per thousand ethanol (61.8+/-7.4 and 53.0+/-8.2% of control). For the first time the present study demonstrates acute inhibitory effects of ethanol on single cardiac sodium channel gating and provides one potential mechanism for the well known clinical observation that ethanol triggers supraventricular and ventricular arrhythmias.